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1. Demystifying SMPS Design
Powered by ST
Rogerio BUENO
March-18th , 2020

2. Demystifying SMPS Design
Powered by ST
Rogerio BUENO
March-18th , 2020

3. Agenda
• Market
• Topologies
• How to implement
• Simulation
• Design tips
• QA
3

4. Periodical
appliances
Behavioral
appliances
Target market
Home Appliances Smart Home Smart Industry
4

5. Trend
Gate
driver
Reference voltage
+
-
Vout
+
-
Ramp VinController IC
Power stage
Compensation
• Main key parameters
• Simple, one operational amplifier and one comparator
needed
• Compensation loop is tuned by changing external
capacitor/resistors
• Gate driver usually implemented in Controller IC
• Number of implemented features are limited, ASIC only
for high volumes
• All actual values of system are measurable by
oscilloscope
Gate
driver
Vout
Timer
Vin
MCU
Power stage
Driving
ADC
Digital
control loop
• Main key parameters
• Require MCU timer with high resolution
• Compensation loop is tuned by constant – this value
can be variable with load/voltage change
• „Controller output - Action command value“ is
measurable at DAC pin by oscilloscope
• Analog • Digital
5

6. Auxiliary Power Supply
How does it look like
Isolated Auxiliary Supply
Voltage Suppressors,
(Zenner, TVS)
Output Diode
Voltage
Controller
Rectifying diodes
Offline
Converter
or Controller
CV
Controller
Opto
HV MOSFET
Off-line Controller
AC
Voltage
DC Voltage
6

7. Topologies
Buck Converter

8. Buck Operation
SW L1
LoadD1
Cout
Rectifier
AC
input
Cin
L1
Load
D1
Reverse
Cout
charging
ON
+
+
-
-
Vd
Vl
Vo
L1
Load
D1
Forward
Cout
discharging
OFF
+
+
-
-
Vd
Vl
Vo
8

9. L1
C1
D1
C2
Q1
L1
C1
D1
C2
Q1
L1
C1
D1
C2
Q1
Buck – operational principle
InputDC
Output DC
+ +
- -
+ -
IQ1
ONphaseOscillation
phase
OFFphase
InputDC
Output DC
+ +
- -
+-
IQ1
InputDC
Output DC
+ +
- -
+ -
IQ1
IQ1
VD1
IL1
ON OFF ON OFF
IQ1
VD1
IL1
ON OFF ON OFF
IQ1
VD1
IL1
ON OFF ON OFF
 
L
VVt
I outinON
L

 1
L
Vt
I outOFF
L  1
9

10. L1
C1 D1 C2
Q1
D2
C3
Buck topology for HV – Other issues to consider
• HS switch => issue with feedback
connection
• The regulation does not sense voltage
directly from output, but from reflection
on C3 => load regulation.
• Low duty cycle
• Due to minimum Turn ON time the
generation of low output voltage can
bring instability or power limitation
• Recovery effect of diode
• The D1 has to be fast diode as possible
to minimize losses due to recovery
effect
• Operation at no load
• For no load the output voltage can rise
up => some minimum load is requested
FB
CTRL.
STTA806
STTH8R06
STTH806
TTI
SiC
VR= 400V ; IF=
8A ; Tj= 125°C
di/dt= 200A/µs
0
2A/Div , 20ns/Div
10

11. Inductor
 Iout is not de max current flowing
through the inductor in a buck
converter. Take into account Imax.
Imin
0
D.T T
t
Imax
Iav
IL
0
tOnOn Off
ToffTon
 Check the ratio Iop/IR x Temperature
Ambient.
 For better efficiency and thermal
behavior check Pc = Rdc * Irms2.
 In addition, considering Imax and max
operating temperature it is
suggestable to keep some margin to
avoid saturation.
11

12. Flyback Theory of Operation

13. Flyback – operational principle
C1
D1
C2
Q1
1 4
2 3
T1
InputDC
Output DC
+ +
-
-
+
+-
-
IQ1
IQ1
VQ1
ID1
ON OFF ON OFF
ONphase
C1
D1
C2
Q1
1 4
2 3
T1
InputDC
Output DC
+ +
-
-
IQ1
VQ1
ID1
ON OFF ON OFF
Oscillation
phase
C1
D1
C2
Q1
1 4
2 3
T1
InputDC
Output DC
+ +
-
-
+
+-
-
ID1
IQ1
VQ1
ID1
ON OFF ON OFF
OFFphase
13

14. Flyback modes of operation
IQ1
VQ1
ID1
ON OFF ON OFF
• Benefits
• ZCS turn ON of MOSFET
• ZCS turn OFF diode
• Drawbacks
• EMI self-oscillating
• Unused time slot
• When to use
• Higher input voltage (typ. 230V)
Discontinuous Mode DCM
IQ1
VQ1
ID1
ON OFF ON OFF
Quasi Resonant Mode
• Benefits
• ZCS turn ON of MOSFET
• ZCS turn OFF diode
• Drawbacks
• Variable frequency could be
problematic
• When to use
• When efficiency is main
parameter
IQ1
VQ1
ID1
ON OFF ON OFF
Continuous Mode CCM
• Benefits
• Higher power capability
• Drawbacks
• Not ZCS – worse EMI and
switching power loses
• When to use
• Need for peak power demands
• When lower input voltages (110V)
14

15. Flyback Topology – Leakage Inductance
• Leakage Inductance
• Leakage inductance is a parasitic inductance
that is in series with primary inductance,
Hence leakage inductance absorbs part of
energy sent to Xmer
• Typically Leakage inductance is 1-3% of
primary inductance, it is mostly a function of
physical structure of transformer
• PLeakage = ½ * LLeakage* Ip
^2 * F
15

16. Flyback Topology – Leakage Inductance 16

17. Flyback Design – Peak Clamp Circuit
Benefits
• Best standby
• Best Efficiency
• Precise voltage limitation
Drawbacks
• Additional load burning power even at
light/no load.
• Peak level depends on the load level.
17

18. How to implement a SMPS ?
From few watts up to 75W

19. Product positioning for AC-DC SMPS
25W
L656x
L6599A, L6699
0W 75W 100W
(Embedded MOS)
VIPerPlus family
Flyback
Converter
Flyback
Controller + ext. MOS
PFC + Flyback PFC + LLC
Power
L6566xx,
HVLED001A,
STCH03
L656x, HVLED001A
STCH03
L6566xx
19

20. >800V
Power MOSFET
Mixed signal
Controller
VIPer PLUS offline converters
Robust and tight technology
Primary
MOSFET
800V
HV current source 800V
Thermal diode
senseFET
20

21. Supported Topologies
VIPer*6, VIPer*1, VIPer0PBuck &
Buck-boost
Flyback with
secondary side
regulation (SSR)
Flyback with
primary side
regulation (PSR)
All VIPer families
Altair0*,
HVLED8**
22

22. 800V/1050V switchers to Best Fit your application
4 W 6 W 7 W 12 W 15 WFly-back Converter
85-265VAc
200 mA 350 mABuck Converter 150 mA
Buck&
Fly-back
Fly-back
Fixed Frequency, Jittering,
Brown-out, 30mW STB
Fixed Frequency, Jittering,
Brown-out, 30mW STB
Quasi Resonant
Brown-out, 30 mW STB
Fixed Frequency, Jittering
30mW STB, E/A inside
5V VCC, Input OVP/UVP, 10mW STB
Fixed Frequency, Jittering, E/A inside
Zero Power Mode, 5V VCC
Fixed Frequency, Jittering, E/A inside
Minimal BoM, 730 BVDSS
Fixed Frequency, Jittering, E/A inside
VIPer0P
VIPer01 VIPer11
VIPer25 VIPer35
VIPer06 VIPer16
VIPer17 VIPer27 VIPer37
VIPer28 VIPer38
VIPer122
VIPer26/VIPer26K 1050 V
500 mA
VIPer31*
* under development, samples available
VIPerPlus Product Portfolio
VIPer222
23

23. VIPer*1 Ecosystem
5V-6W@85-265VAC
• VIN = 85 ~ 265 VAC
• VOUT1= 12V (iso)
• IOUT1 = 0.65 A
5V- 200mA
• VIN = 85 ~ 265 VAC
• VOUT1= 5V (non iso)
• IOUT1 = 0.200 A
• T AM = 60°C
STEVAL-ISA178V1
AN4858
VIPER013XS (30kHz)
Buck converters Fly-back converters
12V 7.8W@85-265VAC
5V-6W@85-265VAC
5V- 350mA
• VIN = 85 ~ 265 VAC
• VOUT1= 5V (non iso)
• IOUT1 = 0.35 A
STEVAL-ISA195V1
AN5081
VIPER115XS (30kHz)
STEVAL-ISA197V1
AN5057
VIPER114LS (60kHz)
STEVAL-ISA196V1
AN5072
VIPER114LS (60kHz)
• VIN = 85 ~ 265 VAC
• VOUT1= 5V (non iso)
• IOUT1 = 0.85 A
STEVAL-ISA177V1
AN4855
VIPER013LS (60kHz)
• VIN = 85 ~ 265 VAC
• VOUT1= 5V (non iso)
• IOUT1 = 1.2 A
Under developent
• VIPer11 eDesign integration
• Fly-back PSR/SSR 15V 1.2A based on VIPER318LD
• Buck 5V-500mA (40-265VAC) based on VIPER319XD
ISOLATED
NON
ISOLATED
NON
ISOLATED
VIPer AC-DC converters
Brochures
Transformer
design
SPICE
Models
5V- 100mA
• VIN = 60 ~ 300 VAC
• VOUT1= 5V (non iso)
• IOUT1 = 0.100 A
• T AM = 60°C
STEVAL-VP013B1B
AN4858
VIPER013BLS (60kHz)
24

24. VIPer122 – Application advantages
STEVAL-V12201B (Buck 15V-200mA)
EMI Average @ 230VAC @ ful load
Small filter
STAND-BY 30 mW EFFICIENCY 80%
25

25. Product positioning for AC-DC SMPS
25W
L656x
L6599A, L6699
0W 75W 100W
(Embedded MOS)
VIPerPlus family
Flyback
Converter
Flyback
Controller + ext. MOS
PFC + Flyback PFC + LLC
Power
L6566xx,
HVLED001A,
STCH03
L656x, HVLED001A
STCH03
L6566xx
26

26. STCH03 Quasi Resonant Flyback Controller

27. STCH03 Quasi Resonant Flyback Controller
Offline PWM controller for low standby adapters
• Constant current mode (CC)
from primary side and voltage
control from secondary side
• 650V embedded HV start-up
circuit
• Quasi-resonant (QR) Zero
Voltage Switching (ZVS)
operation
• Valley skipping at medium-light
load and advanced burst mode
operation at no-load
• Accurate adjustable output OVP
and UVP
• SO8 package
Features
• Low part count. BOM reduction
thanks to an extensive features
integration
• Exceeding 5 stars: No-Load
power < 10mW
• HV start-up zero power
consumption
• Advanced burst-mode
operation
• Flexibility: suitable for adapters
from 5W to 65W
• High Efficiency
• Low EMI design: intelligent jitter
for EMI suppression
Benefits
28

28. Quasi-resonant - benefit
For Example: Cd = 100pF, f = 60kHz
P = 0.75W
VD-S
Vsw
500V
P=0.03W
VD-S
Vsw
100V
P = 0.27W
VD-S
Vsw
Vsw
300V
VD-S
𝑃𝐶 𝑙𝑜𝑠𝑠𝑒𝑠
=
1
2
𝑉𝑆𝑊
2
𝐶 𝑑 𝑓
29

29. STCH03 Quasi Resonant Flyback Controller
Pin Connection and Functions
HV PIN:
650V embedded HV
start-up
30

30. STCH03 Quasi Resonant Flyback Controller
Pin Connection and Functions
HV PIN:
650V embedded HV
start-up
ZCD PIN:
Valley detection and
output voltage sensing
31

31. STCH03 Quasi Resonant Flyback Controller
Pin Connection and Functions
HV PIN:
650V embedded HV
start-up
ZCD PIN:
Valley detection and
output voltage sensing
GND PIN
32

32. STCH03 Quasi Resonant Flyback Controller
Pin Connection and Functions
HV PIN:
650V embedded HV
start-up
FB PIN:
Integrated resistor compensation
for CC and CV mode
ZCD PIN:
Valley detection and
output voltage sensing
GND PIN
33

33. STCH03 Quasi Resonant Flyback Controller
Pin Connection and Functions
HV PIN:
650V embedded HV
start-up
FB PIN:
Integrated resistor compensation
for CC and CV mode
ZCD PIN:
Valley detection and
output voltage sensing
SENSE PIN:
Integrated Leading Edge
Blanking time. No low pass
filter required
GND PIN
34

34. STCH03 Quasi Resonant Flyback Controller
Pin Connection and Functions
HV PIN:
650V embedded HV
start-up
FB PIN:
Integrated resistor compensation
for CC and CV mode
ZCD PIN:
Valley detection and
output voltage sensing
SENSE PIN:
Integrated Leading Edge
Blanking time. No low pass
filter required
GD PIN
GND PIN
35

35. STCH03 Quasi Resonant Flyback Controller
Pin Connection and Functions
HV PIN:
650V embedded HV
start-up
FB PIN:
Integrated resistor compensation
for CC and CV mode
ZCD PIN:
Valley detection and
output voltage sensing
SENSE PIN:
Integrated Leading Edge
Blanking time. No low pass
filter required
GD PIN
VDD PIN:
Adaptive UVLO threshold
GND PIN
36

36. STCH03 Quasi Resonant Flyback Controller
Operating Mode
Output characteristic
VOUT
IOUT
CV
CC
Hiccup mode
37

37. STCH03 Quasi Resonant Flyback Controller
Operating Mode
Output characteristic
VOUT
IOUT
CV
CC
Hiccup mode
CV (Constant Voltage Mode) components
FB loop via optocoupler
38

38. STCH03 Quasi Resonant Flyback Controller
Operating Mode
Output characteristic
VOUT
IOUT
CV
CC
Hiccup mode
CV (Constant Voltage Mode) components
FB loop via optocoupler
CC (Constant Current Mode) components
IOUT =
NPRI
NSEC
Ki
2RSENSE
39

39. STCH03 Quasi Resonant Flyback Controller
Operating Mode
Quasi resonant / Multi-mode operation 1/3
VOUT
IOUT
CV
CC
Hiccup mode
VDS
40

40. STCH03 Quasi Resonant Flyback Controller
Operating Mode
Quasi resonant / Multi-mode operation 2/3
VOUT
IOUT
CV
CC
Hiccup mode
VDS
41

41. STCH03 Quasi Resonant Flyback Controller
Operating Mode
Quasi resonant / Multi-mode operation 2/3
VOUT
IOUT
CV
CC
Hiccup mode
VDS
42

42. STCH03 Quasi Resonant Flyback Controller
Functions and Protections
Frequency Jittering
VDS
JITTERING EFFECT
43

43. STCH03 Quasi Resonant Flyback Controller
Functions and Protections
Frequency Jittering
Feedforward
compensation
RZCD =
NAUX
NPRI
LPRIRFF
TDRSENSE
44

44. STCH03 Quasi Resonant Flyback Controller
Functions and Protections
Overvoltage and
Undervoltage Protection
Feedforward
compensation
ROVP =
VOVP
NAUX
NPRI
VOUT−OVP − VOVP
RZCD
𝑉OUT−UVP =
NSEC
NAUX
(ROVP+RZCD)
ROVP
VUVP
Frequency Jittering
45

45. STCH03 Quasi Resonant Flyback Controller
Functions and Protections
Overvoltage and
Undervoltage Protection
Thermal Shutdown
Protection
Feedforward
compensation Frequency Jittering
46

46. STCH03 Quasi Resonant Flyback Controller
Functions and Protections
Overcurrent
Protection
Frequency Jittering
Feedforward
compensation
Overvoltage and
Undervoltage Protection
Thermal Shutdown
Protection
47

47. Offline Auxiliary Power Supply design with STCH03
HV Power Mosfet Selection
VDS
VIN
Input voltage
VINMAX = 265VAC * 1.414 = 380V
48

48. Offline Auxiliary Power Supply design with STCH03
HV Power Mosfet Selection
Reflected Voltage
VR = nVOUT =
D
(1 − D)
VIN
VR = 50 ÷ 200V typically
VDS
VR
VIN
VR
VR
Input voltage
VINMAX = 265VAC * 1.414 = 380V
49

49. Offline Auxiliary Power Supply design with STCH03
HV Power Mosfet Selection
Reflected Voltage
VR = nVOUT =
D
(1 − D)
VIN
VR = 50 ÷ 200V typically
Leakage inductance spike
Limited by clamp circuit
VSPIKE = 50 ÷ 200V typically
VDS
VSPIKE
VR
VIN
VR
VR
Input voltage
VINMAX = 265VAC * 1.414 = 380V
50

50. Offline Auxiliary Power Supply design with STCH03
HV Power Mosfet Selection
Reflected Voltage
VR = nVOUT =
D
(1 − D)
VIN
VR = 50 ÷ 200V typically
Leakage inductance spike
Limited by peak calm circuit
VSPIKE = 50 ÷ 200V typically
Margin
VMARGIN = 10 ÷ 30% typically
VDS VMARGIN
VSPIKE
VR
VIN
DRAIN SOURCE BREAKDOWN VOLTAGE
VR
VR
Input voltage
VINMAX = 265VAC * 1.414 = 380V
51

51. Offline Auxiliary Power Supply design with STCH03
HV Power Mosfet Selection
Reflected Voltage
VR = nVOUT =
D
(1 − D)
VIN
VR = 50 ÷ 200V typically
Leakage inductance spike
Limited by peak calm circuit
VSPIKE = 50 ÷ 200V typically
Margin
VMARGIN = 10 ÷ 30% typically
VDS VMARGIN
VSPIKE
VR
VIN
DRAIN SOURCE BREAKDOWN VOLTAGE
VR
VR
VS VMVRVIN
Input voltage
VINMAX = 265VAC * 1.414 = 380V
SUM
#1 380V + 50V + 50V + 100V = 580V
M5 650V
52

52. Offline Auxiliary Power Supply design with STCH03
HV Power Mosfet Selection
Reflected Voltage
VR = nVOUT =
D
(1 − D)
VIN
VR = 50 ÷ 200V typically
Leakage inductance spike
Limited by peak calm circuit
VSPIKE = 50 ÷ 200V typically
Margin
VMARGIN = 10 ÷ 30% typically
VDS VMARGIN
VSPIKE
VR
VIN
DRAIN SOURCE BREAKDOWN VOLTAGE
VR
VR
VS VMVRVIN
Input voltage
VINMAX = 265VAC * 1.414 = 380V
SUM
#1 380V + 50V + 50V + 100V = 580V
#2 380V + 100V + 100V + 200V = 780V
M5 650V
K5 800V
53

53. Mosfets - SuperJunction MDmeshTM
M5, M2,DM2 & K5
54
• M5: the leading
technology for hard
switch
Key Features
• Industry’s one of the
lower RDS(on) in the
Market
• High switching speed
• 650V BVdss rated
Benefit
• highest efficiency in the
application
• Smaller form factor of
final system
• Especially targeted for
hard switching (PFC,
Boost, TTF, Flyback)
M6/ M2 / M2 EP: best for
LLC
Key Features
• Up to 30% lower Qg
(equivalent die size)
• 400 – 700V Bvdss rated
• Back-to-Back G-S zener
protected
Benefit
• Reduced switching losses
through optimized (Qg)
(Ciss, Coss)
• Enhanced immunity vs
ESD & Vgs spikes in the
application
• Especially targeted for HB
LLC, TTF, Flyback..)
• M2 EP Tailored for Very
High Frequency
Converters (f > 150 kHz)
DM2 DM6 Fast Diode:
best F/B ZVS
Key Features
• Integrated fast body diode
• Softer commutation
behavior
• Back-to-Back G-S zener
protected
Benefit
• Reduced switching losses
through optimized (Qg)
(Ciss, Coss)
• High peak diode dV/dt
capabilities
• Best use in Full Bridge
ZVS
K5: best in class Very
High Volt.
Key Features
• Extremely good RDS(on) at
very high BVDSS
• High switching speed
• 800-950V BVDSS rated
• ted fast body diode
Benefit
• High efficiency with lower
design complexity
• Especially targeted for
flyback LED topologies and
high voltage range in the
application
STW55NM60N
STWxxN60DM2
Products & Applications
54

54. How to select the right Power MOSFET
Maximum Ratings
 Represent the extreme capability of the devices
 To be used as worst conditions that the design should
guarantee will not be exceeded.
 Vds, RDS(on), Id, dv/dt (diode), SOA, Rth, package type are
some of the most used parameters to identify the right MOSFET
.
MOSFET (IGBT) Finder App
 Selection Guide in PDF
 ST WEB page
 The new MOSFET Finder App is even
smarter and user friendy tool
DS is needed to fine tune the rough preliminary selection
55

55. Offline Auxiliary Power Supply design with STCH03
Rectifiers for Secondary Side
SR
Controller
56

56. Offline Auxiliary Power Supply design with STCH03
Rectifiers for Secondary Side: DIODE
VOUT
VOUT
VOUT
VR
Output Voltage
57

57. Offline Auxiliary Power Supply design with STCH03
Rectifiers for Secondary Side: DIODE
VIN/n
VOUT
VOUT
VOUT
VR
Forwarded Voltage
VIN
n
= VOUT 1 +
VIN
VR
Output Voltage
58

58. Offline Auxiliary Power Supply design with STCH03
Rectifiers for Secondary Side: DIODE
VSPIKE
VIN/n
VOUT
VOUT
VOUT
VR
Spike
VSPIKE typically negligible
Forwarded Voltage
VIN
n
= VOUT 1 +
VIN
VR
Output Voltage
59

59. Offline Auxiliary Power Supply design with STCH03
Rectifiers for Secondary Side: DIODE
VMARGIN
VSPIKE
VIN/n
VOUT
VOUT
VOUT
VR
BREAKDOWN VOLTAGE
Margin
VMARGIN = 10 ÷ 30% typically
Spike
VSPIKE typically negligible
Forwarded Voltage
VIN
n
= VOUT 1 +
VIN
VR
Output Voltage
60

60. Offline Auxiliary Power Supply design with STCH03
Rectifiers for Secondary Side: DIODE
IFAV
VRR
M
SignalSchottky
diodes
Power Schottky diodes
Field-effect
rectifiers
SiC diodes
Ultrafast bipolar rectifiers
VMARGIN
VSPIKE
VIN/n
VOUT
VOUT
VOUT
VR
BREAKDOWN VOLTAGE
Margin
VMARGIN = 10 ÷ 30% typically
Spike
VSPIKE typically negligible
Forwarded Voltage
VIN
n
= VOUT 1 +
VIN
VR
Output Voltage
61

61. Offline Auxiliary Power Supply design with STCH03
Rectifiers for Secondary Side: DIODE
IFAV
VRR
M
SignalSchottky
diodes
Power Schottky diodes
Field-effect
rectifiers
SiC diodes
Ultrafast bipolar rectifiers
VMARGIN
VSPIKE
VIN/n
VOUT
VOUT
VOUT
VR
BREAKDOWN VOLTAGE
Margin
VMARGIN = 10 ÷ 30% typically
Spike
VSPIKE typically negligible
Forwarded Voltage
VIN
n
= VOUT 1 +
VIN
VR
VS VMVIN/nVOUT
+
+
+
+
+
+
+
+
+
= 36V
= 119V
= 238V
5V
24V
48V
20V
60V
120V
2V
5V
10V
9V
30V
60V
#1
#2
#3
SUM
FERD 45V
PS 150V
UF 300V
Output Voltage
62

62. Diode selection
New simple mobile-app to find your diode
63

63. Synchronous rectification in Flyback

64. Typical schematics & product mapping
Flyback with Schottky diode
85 – 265 Vac
Vout
PWM
controller
STPSx40,60,100, FERD
Power Schottky & FERD diodes
+
65

65. Typical schematics & product mapping
Flyback with Synchronous Rectifier
SRK1000
85 – 265 Vac
Vout
PWM
controller
SRK1000
SR controller
MOSFET 40-120V
F7 series MOSFET
+
66

66. SRK1000
• Suitable for Flyback in QR (Quasi Resonant) or
DCM/CCM FF (Fixed Frequency) Mode of Operation
• High efficiency & low Stand-by
• Can Drive Standard Level SR MOSFET
• Low consumption mode management
• Small Package: SOT23-6
New Synchronous Rectification Controller for Flyback
SRK1000*
Feedback
PWM
Controller
67

67. Offline Auxiliary Power Supply design with STCH03
Rectifiers for Secondary Side: SYNCHRONOUS RECTIFICATION
SRK1000
Adaptive SR
Controller
STCH03
68

68. Offline Auxiliary Power Supply design with STCH03
Rectifiers for Secondary Side: SYNCHRONOUS RECTIFICATION
SRK1000
Adaptive SR
Controller
STCH03
STripFET F7
Power Mosfet
69

69. Offline Auxiliary Power Supply design with STCH03
Rectifiers for Secondary Side: SYNCHRONOUS RECTIFICATION
VMARGIN
VSPIKE
VIN/n
VOUT
VOUT
VOUT
VDS
BREAKDOWN VOLTAGE
Margin
VMARGIN = 10 ÷ 30% typically
Forwarded Voltage
VIN
n
= VOUT 1 +
VIN
VR
VS VMVIN/nVOUT
+ + + = 80V5V 43V 20V 12V#1
SUM
STL90N10F7
STL90N10F7
Output Voltage
Leakage inductance spike
Limited by peak calm circuit if necessary
VSPIKE = 10 ÷ 50V typically
70

70. SRK1000 & SRK1001
Flyback
QR & DCM/CCM FF
SRK1000
SRK1001
SRK1000
DVS AMR 100V
SOT23-6L
SRK1001
DVS AMR 185V
SO8
DVS AMR100V 185V
production production
71

71. SRK1000* family Ecosystem
• Datasheet  available
• Daughter Boards  available
• AN  AN5066
BOARD MOSFET PACKAGE Controller
EVLSRK1000-TO 100V – 10mW TO220FP SRK1000
EVLSRK1000-DP 100V – 10mW DPAK SRK1000
EVLSRK1000-PF 100V – 8mW PwFlat 5x6 SRK1000
EVLSRK1000-PF3 60V – 6.2mW PwFlat 3.3x3.3 SRK1000
EVLSRK1000A-TO 100V – 10mW TO220FP SRK1000A
EVLSRK1000A-PF 100V – 8mW PwFlat 5x6 SRK1000A
EVLSRK1000B-TO 100V – 10mW TO220FP SRK1000B
EVLSRK1000B-PF 100V – 8mW PwFlat 5x6 SRK1000B
72

72. Features
&
Benefit.
Extremely Low RDS(on)
Low conduction losses
Optimized body diode (low Qrr)
Excellent switching perfomance
Optimal capacitance Crss/Ciss
No EMI issue
.
Extremely low thermal resistance
High current capability and Power dissipation
Several package solutions
Wide product portfolium
STripFET F7 series highlight
40V ÷ 120V
BVDss
LV BU
73

73. EVLSTCH03-36W-SR
36W USB Power adapter with STCH03
• Universal input mains voltage range: from 90 Vac to 264 Vac
• Three fixed Vout available: 5 V, 9 V, 12 V @ 3 A continuous operation
• Load power limited to 35 W & 3A out
• CV regulation with optocoupler and CC regulation with primary side sensing
• Synchronous rectification with SRK1000
• OVP, UVP, OC, short-circuit protections
• Compact design: 73x56x18 mm
74

74. Thermal results
With synchronous rectification With Schottky diode
MOSFET – 52.4°C
PowerFLAT 5x6
Schottky – 112°C
PowerFLAT 5x6
Remarks: 23°C ambient, 230Vin, output : 9V; 3.0A; 27W
75

75. Evaluation Boards

76. Evaluation boards
STEVAL-SMACH15V1
15W board: 35mmx44mm
(USB connector included)
EVLSTCH03-36W-SR 36W
board: 5-9-12V @ 3A
STCH03L+SRK1000B
73mmx55mm
EVAL-STCH03-45WPD
45W USB TyPe-C PD
STCH03+STUSB4761+SRK1001
70mmx50mm
Currently under development
Covering all
chargers and
adapters
flavors
EVAL-STCH03-45W
45W/12V board
STCH03+SRK1000B
85mmx55mm
Databrief Available
STEVAL-USBPD45C
45W USB TyPe-C PD
STCH03+STM32F051
73mmx51mm
77

77. Offline Auxiliary Power Supply design with
STCH03

78. Specifications
Actuals view
Analysis
diagrams
A fully
annotated
and
interactive
schematic
Interactive
BOM
A full set of commands
Customize
the Flyback
transformer
..never so easy make a SMPS design
eDesignSuitehttps://my.st.com/analogsimulator/
79

79. Design tips

80. Transformer tips 81

81. Transformer tips 82

82. Layout tips 83

83. Basic Hints for Lp and n Selection
• Main parameters: input voltage range,
switching frequency and current limitation.
• Set Lp and n for minimum input voltage to
use maximum of time slot.
• Set Lp to be lower (10 – 15%) than the peak
current limit of driving circuit (OCP).
• Set n to keep enough margin for the Mosfet.
• Set n to keep optimal diode voltage.
Viper+ allows to
select the max
peak current level
in fine way
Viper+ includes
800V MOSFET =
more freedom for
designing
84

84. Input data, basic equitation
Design – Input data:
85

85. DCM x CCM
DCM Operation CCM Operation
Pin = 9W Pin = 9W
Lp=1.68mH Lp=5.0mH
Ippk=422mA Ippk=280.5mA
Iprms=169mA Iprms=112mA
 Higher I2R losses  Lower conduction losses
 Bigger input filter for EMI  Smaller input filter for EMI
 Bigger output capacitor  Smaller output capacitor
 Smaller Transformer  Bigger Transformer
 Lower cost secondary side rectifier  Higher cost secondary side rectifier
 One pole: easy to compensate  Two poles+RHP zero: instability possible
86

86. Very useful references
AN1262
OFFLINE FLYBACK CONVERTERS
DESIGN METHODOLOGY
AN1326
L6565 QUASI-RESONANT
CONTROLLER
87

87. Where to buy ST ? 88

88. Finders app 89

89. How can I get support ?

90. OLS- Entre no site www.st.com
- Acesse sua conta
- uma vez “logado”, siga a sequência abaixo:
91

91. OLS
E então:
https://www.st.com/content/st_co
m/en/support/support-home.html
92

92. QA session
• Questions -> chat
• Gifts  for two best questions :
STEVAL-ISA177V1
STEVAL-ISA174V1
93

93. stmicroelectronics.brasil@st.com
94